1. Field of the Invention
The present invention relates to a holder for holding a small-sized acoustic element, such as a receiver, a speaker, or a buzzer, contained in a portable communication apparatus, such as a mobile phone, a PHS, or a PDA with a communicating function, and to a mounting structure for the holder.
2. Description of the Related Art
FIG. 6 shows a conventional mobile phone 1 having a casing 4 composed of a front cover 2 and a rear cover 3, with the casing 4 having on its front surface 4a an input operation section with a plurality of pushbutton keytops 5 for input operation and a display screen 6 above the input operation section. Above the display screen 6, there is formed a sound hole 7 in the form of a through-hole for emitting sound outwards from a built-in receiver (not shown). Below the pushbutton keytops 5, there is formed above a microphone 8 as a built-in “small-sized acoustic element” a microphone hole 9 situated in the form of a through-hole adapted to introduce the voice of the user.
The microphone 8 has a substantially disc-like general configuration, and is, as shown in FIG. 7, accommodated in a microphone holder 10. The microphone holder 10 is accommodated in a holder mounting input operation section 2b formed as a recess in the back surface 2a of the front cover 2. In this mounting structure, the sound receiving surface 8a of the microphone 8 faces the back surface 2a, and the voice V transmitted through the microphone hole 9 reaches the sound receiving surface 8a, thereby achieving an enhancement in sensitivity in sound gathering. That is, the direction perpendicular to the sound receiving surface 8a is matched with the hole axis of the microphone hole 9 to thereby enhance sensitivity in sound gathering.
As shown in FIG. 8, the microphone holder 10 has a cylindrical portion 10a retaining the entire outer peripheral surface 8b of the microphone 8. The cylindrical portion 10a is closed at one end by a bottom portion 10b, which has four elastic connector portions 10c in the form of columnar protrusions protruding from both sides thereof. Formed in the elastic connector portions 10c are conduction paths (not shown) in which conductive powder, granules, or linear bodies are arranged in the thickness direction by a magnetic force, and the four electrodes 8c of the microphone 8 are electrically connected to corresponding board electrodes 11a of a printed circuit board 11 through these conduction paths. At the other end of the cylindrical portion 10a, there is formed an inwardly directed flange 10d, which retains the outer edge of the sound receiving surface 8a of the microphone 8 over the entire periphery thereof. In a complete mounted state shown in FIG. 7, the inwardly directed flange 10d is pressurized by the back surface 2a of the front cover 2, whereby the microphone 8 is pressurized downwardly as seen in the drawing, making the electrical contact of the electrode 8c of the microphone 8 with the board electrodes 11a through the conduction paths of the elastic connector portions 10c more reliable. A conventional example of the microphone holder 10 as described above and the mounting structure for the same is disclosed in JP 2001-333481 A (FIGS. 1(3) and 2(3)).
Incidentally, the entire length L of the above-described conventional mobile phone 1 is not always large enough to allow the microphone hole 9 to reach the mouth of the user while the sound hole 7 is being applied to the ear. That is, the length is relatively small, causing the microphone hole 9 to be situated at a position near the cheek or the chin of the user. As a result, the user may inadvertently clog the microphone hole 9 with his cheek or chin during conversation. To solve this problem, a design has been conceived in which a microphone hole 12 is formed not in the front surface 4a of the casing 4 but in the bottom surface 4b thereof as in this particular conventional example.
However, as shown in FIG. 9, when there is adopted a mounting structure in which the microphone hole 12 is formed in the bottom surface 4b and in which the hole axis of the microphone hole 8 is matched with the direction perpendicular to the sound receiving surface 8a of the microphone 8 to achieve higher sensitivity in sound gathering, the thickness t2 of this structure has to be substantially increased as compared with the thickness t1 of the mobile phone 1 shown in FIGS. 6 through 8. And, this problem is experienced not only in the mobile phone 1 as shown, but also in various portable communication apparatuses, such as a collapsible mobile phone, a PHS, a transceiver in which the microphone hole is provided not in the front surface of the casing but in one of the side surfaces connected to the front surface. Further, this applies not only to the mounting structure for the microphone but also to the mounting structure for various small-sized acoustic elements, such as a receiver and a buzzer.